OPTICAL SCANNING DEVICE AND IMAGE FORMING APPARATUS

PROBLEM TO BE SOLVED: To suppress imbalance of image misalignment between a plurality of beams in the direction perpendicular to a deflecting and scanning direction, occurring between the beams at the scanning-start-side edge of the target surface and those at the scanning-end-side edge, and to suppress the degradation to the formed image caused by the imbalance of image misalignment. SOLUTION: The optical scanning device includes: a first optical system of lenses 2 to 5 that shapes a plurality of beams of light emitted from a light source 1 that has a plurality of luminous points; a rotary polygon mirror 6 that deflects and scans the beams of light; and lenses 8 to 12 of an optical scanning system that causes the beams of light deflected and scanned with a deflecting faces 6a of the rotary polygon mirror to form images on a surface to be scanned 13a. The main beams of the beams of light are made incident to the deflecting face having respectively different angles with respect to the optical axis m of the optical scanning system within the deflecting/scanning surface, wherein βis assumed to be half of an angle formed between the optical axis n of the first optical system and the optical axis m of the optical scanning system within the deflecting/scanning surface, δ is assumed to be a distance from an intersection dc of the optical axis n and the deflecting face to an intersection hh of the intersection of a normal line, when the angle formed between the optical axis n and the normal line drawn from the rotary center of the rotary polygon mirror to the deflecting surface is β, wherein δ is set to be zero or a negative value, given that δ is defined positive when the intersection dc is present on the optical-scanning side of the intersection hh. COPYRIGHT: (C)2011,JPO&INPIT